Riot police fired tear gas and water canons at crowds during today's unauthorized student protests over educational costs in the Chilean capital of Santiago.

Students set up barricades of burning tires around the city this morning and threw rocks at approaching army tanks trying to put out the fires.

Hundreds of protesters were detained by riot police as they tried to march on the Plaza de Armas in the city center.

In Chile, public schools are owned by municipalities instead of the state and, therefore, the quality of education varies based on location.

Students want public universities to be government-owned and free of charge.

"The education system in Chile is one of the most expensive in the world, according to the OECD (Organisation for Economic Cooperation and Development)," said 21-year-old law student Rodrigo Fuentes. "That's why we're protesting. We have countries in South America that have free public education, but we pay a lot to study in the public university. We think that's very unfair because we don't have the money, especially right now."

During a second protest this evening, students holding banners began marching on Plaza Italia.

Young men beat relentlessly on congo drums. Several marched in the middle of the street, causing clashes with rush hour traffic.

Within 10 minutes, riot police arrived in tanks and began firing tear gas on the crowd. Students covered their mouths and ran as tears ran down from their bloodshot eyes.

One girl came to this evening's riot prepared with two large bags of lemons. As she handed out lemon halves, students began biting into them to ease the tear gas' burning sensation.

For weeks, more than 100,000 students, most of whom are at the undergraduate or high school level, have been protesting on the streets of Santiago.

Up until today, they were given government permits to protest and were working with Chilean President Sebastian Pinera on education reforms.